The present invention relates to an optical disk recording/reproducing method and, more particularly, to an optical disk recording/reproducing method which can be suitably applied to an optomagnetic disk recording/reproducing apparatus.
Conventional optomagnetic recording systems are classified into an optical modulating system in which a laser beam as recording light to be radiated on an optomagnetic recording medium is modulated on the basis of an information signal to be recorded, and a magnetic field modulating system in which an external magnetic field to be applied on an optomagnetic recording medium is modulated on the basis of an information signal to be recorded.
In an optomagnetic disk recording/reproducing apparatus of the magnetic field modulating system, a light beam emitted from a laser light source such as a semiconductor laser element is radiated to be focused on a recording medium of an optomagnetic disk by an objective lens of an optical pickup, thereby locally increasing a temperature as compared with a non-irradiated portion. In addition, a modulated magnetic field corresponding to an information signal to be recorded is applied to the optomagnetic disk by external magnetic field generating means, thereby inverting the magnetic domain of a vertical magnetic recording film as an optomagnetic recording medium of the optomagnetic disk and recording desired data.
Upon reproduction, switching control is performed so that a light amount of the light beam emitted from the laser light source is reduced to be smaller than that upon recording, and then the light beam is radiated on an optomagnetic disk. A light beam reflected by the optomagnetic disk is detected by a photodetector of the optical pickup, and data recorded on the optomagnetic disk is reproduced on the basis of the detection result.
In such a conventional optomagnetic disk recording/reproducing apparatus, the operability (use convenience) can be significantly improved by increasing a data transfer speed. In order to increase the data transfer speed, a rotational speed obtained by rotary driving means such as a spindle motor for an optomagnetic disk must be set high. Upon recording, it is desired that a switching speed for a modulated magnetic field generated from external magnetic field generating means is increased and a light amount of the light beam emitted from the laser light source is increased in correspondence with the increased rotational speed. Upon reproduction, it is desired to increase a signal processing speed for a detection signal output from the photodetector.
If, however, the switching speed for a modulated magnetic field (this modulated magnetic field is based on an information signal to be recorded generated from the external magnetic field generating means) is set high, a magnetic head as the external magnetic field generating means for generating the modulated magnetic field generates heat. Also, power consumption of a magnetic head driver is increased. In addition, it is difficult to increase a light amount of a light beam emitted from a semiconductor laser element as a laser light source upon recording. Therefore, it is difficult to increase the data transfer speed beyond a conventional speed with conventional techniques.